An opinion poll carried out for BBC News Online suggests that almost half of Britons over the age of 18 want to see the use of cannabis decriminalised.

And in the south of the country there is now a majority in favour of changing the law.

ICM Research conducted the survey across England, Scotland and Wales, questioning a random selection of 1,000 people by telephone.

Forty-nine per cent said they thought that using the drug should no longer be a criminal offence. But there were some sharp differences according to age.

Not surprisingly perhaps, the greatest support for change was amongst the young. In the 18-24 age group, 62% said they wanted the law to be changed.

The least enthusiasm was among the over 65s, with only 33% in favour.

Treatment

People in social class AB were more receptive to the idea (54%), as were those in the South of the country (51%).

The survey also asked if people who use drugs, but not those who deal in drugs, should be encouraged by the courts to accept treatment as an alternative to being sent to prison.

Four out of five people questioned in the survey said they agreed with the idea.

The results of the opinion poll may be seen as evidence of a gradual shift in public attitudes, although many politicians remain opposed to a liberalisation of the law.

A survey last October revealed that a greater percentage of UK adults use cannabis than in any other country of the European Union.

One in ten British adults use the drug, or have done in the last 12 months, the European Union Drugs Agency figures suggested.

And the problem is also common in schools, where almost half of all pupils have tried cannabis by the time they leave.

'Pragmatic'

The Liberal Democrats want an advisory body to be set up to look at the way drugs are classified and to see whether the law needs to be changed.

"I think public opinion has moved on considerably," says the party's Home Affairs spokesman Simon Hughes.

"I think public opinion is also being pragmatic and saying, well, I might not want to use it myself, but this should not be a policing priority, and there are many things we want the police to do, and many crimes we want them to deal with, and actually people using cannabis for recreational activities isn't anywhere near the top of our list."

Simon Hughes: Review needed

Mr Hughes says the question is not just whether using cannabis should no longer be a criminal offence, but whether it should be legitimate to sell it and buy it.

"Some of the recommendations are that you allow people to use it, without it being regarded as committing a criminal offence, but you still regard it as a crime to sell.

"I think that is a difficult policy to sustain and a government, if it was going to move the law in the direction the poll suggests the public might now be ready for, ought to be honest and say it would be nonsense to have it legitimately used but not legitimately bought and sold."

Fines

Last October, the Shadow Home Secretary, Ann Widdecombe, advocated £100 on-the-spot fines for anyone caught in possession of cannabis. But the Tories then suffered the embarrassment of several members of the Shadow Cabinet admitting they had smoked the drug in their youth.

Nevertheless, Miss Widdecombe remains firmly opposed to any move that would make cannabis freely available.

"We've got two legal drugs, cigarettes and alcohol, and we've got massive problems with both of them," she argues. "Why add a third drug to the legal list?"

Ann Widdecombe: Zero tolerance

She says soft drugs could be a factor in many road accidents, and can also exacerbate mental health problems for users.

"Cannabis is also a cause of crime, and I would ask that 49% this question: 'If you legalise soft drugs what do you think the drugs barons are going to do? Are they going to go home, or are they going to put all their efforts into marketing hard drugs and targeting the young in particular? Which is it going to be?'"

The Prime Minister, Tony Blair, has made it clear he has no plans to change the law on cannabis. Last November his anti-drugs co-ordinator, Keith Hellawell, said new research showed it was a "gateway drug" that led onto substances like heroin and cocaine.

"The argument for the legalisation of cannabis is dead," said Mr Hellawell.

But others disagree. The former chief constable of Gwent, Francis Wilkinson, is the patron of Transform, an organisation lobbying for reform of the drugs laws. He says it is time that cannabis was debated, demystified and decriminalised.

I think public opinion has moved on considerably

Simon Hughes MPLiberal Democrat

After the high profile Tory admissions, 250 financial directors were asked whether they had tried cannabis in a survey by Accountancy Age. A total of 33% said they had.

Home Office figures from the 1998 British Crime survey also suggest that a large proportion of the UK's adult population have experimented with illegal substances.

The results indicate that a third of people aged between 16 and 59 have tried drugs at some time, while almost half of those aged between 16 and 29 have done so.

Statistics also show that in 1998, more than 97,000 people were arrested for misuse of cannabis - a leap from about 26,000 in 1988.

The proportion of people cautioned over the drug rose from 36% to 54% in the same period.